Read and explained 
1) Learning and Knowledge
The first two terms we will examine are knowledge and learning. Knowledge is defined as the possession of information or the possession of the ability to locate desired information. In the 1700s, Samuel Johnson, compiler of the first comprehensive English-language dictionary, wrote, ''Knowledge is of two kinds: we know a subject ourselves, or we know where we can find information upon it.''

Learning is the process of acquiring knowledge. It's the general term used for a group of activities that result in behavior or information being gained or modified. This distinction is important, because learning information is not the end of the matter. The world of information is constantly changing, faster today than ever before, so it is vital that we realize our knowledge base must be kept up-to-date.

Jane has a vast knowledge base; after all, she graduated from medical school! She recognizes, however, that the process of learning never stops. She regularly attends continuing education classes and there learns about new discoveries, treatments and techniques to benefit her patients.

2) Performance and Memory
Acquiring knowledge through the process of learning is useless if that knowledge is not put to use! Performance is what you do with the knowledge you have. It's especially important to be able to generalize, or take information gained in one setting and apply it to another.
For Jane, performance takes the form of treating patients. She generalizes when, for example, she examines a patient's ear and sees redness and swelling. She doesn't have to have had a specific course recently on otology, or the treatment of ears, to know this may point to the presence of an infection. She can use her general knowledge about signs and symptoms to make an educated guess and then choose the proper tests to run to confirm or reject her theory.

Memory is the ability to retain knowledge in the brain. A good memory is one of the tools needed to be a good learner, though only one. As Samuel Johnson noted, it's not always essential to remember information if you can remember where to find it.

Cognition 
Cognition is defined as ‘the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses.’ Cognition is seen look as the mental processes relating to the input and storage of information and how that information is then used to guide your behaviour.

 It is in essence, the ability to perceive and react, process and understand, store and retrieve information, make decisions and produce appropriate responses. 

The modern word ‘cognition’ actually has its roots back to Latin, the word ‘cognoscere’ which is to ‘get to know’. With that in mind, cognitive functioning is therefore critical for day-to-day life, governing our thoughts and actions. We need cognition to help us understand information about the world around us and interact safely with our environment, as the sensory information we receive is vast and complicated: cognition is needed to distill all this information down to its essentials.

3) What role does cognition have?
Cognition has a physical basis in the brain with over 100 billion nerve cells in a healthy human brain. Each of these can have up to 10,000 connections with other nerve cells called neurons. All of this makes it an incredibly complicated organ. In order to begin to understand the brain we sometimes rely on simplified scientific models, some of which have been developed using studies in rodents and non-human primates. These studies help us better understand certain parts of our cognition, such as how we learn language, and have also been the basis for many breakthroughs in treatments for common disorders of cognition such as Alzheimer’s disease. 

Cognition fundamentally controls our thoughts and behaviors and these are regulated by discrete brain circuits which are underpinned by a number of neurotransmitter systems.

Language and activation 
Research into how multilingual people juggle more than one language in their minds is complex and sometimes counterintuitive. It turns out that when a multilingual person wants to speak, the languages they know can be active at the same time, even if only one gets used. These languages can interfere with each other, for example intruding into speech just when you don't expect them. And interference can manifest itself not just in vocabulary slip-ups, but even on the level of grammar or accent.
From research we know that as a bilingual or multilingual, whenever you're speaking, both languages or all the languages that you know are activated. For example, when you want to say 'dog' as a French-English bilingual, not just 'dog' is activated, but also its translation equivalent, so 'chien' is also activated.

Inhibition 
As such, the speaker of two or more languages needs to have some sort of language control process. If you think about it, the ability of bilingual and multilingual speakers to separate the languages they have learned is remarkable. How they do this is commonly explained through the concept of inhibition – a suppression of the non-relevant languages. When a bilingual volunteer is asked to name a colour shown on a screen in one language and then the next colour in their other language, it is possible to measure spikes in electrical activity in parts of the brain that deal with language and attentional awareness.