Hi Edward,
If you have a context where you heard or saw the word, it would help to explain to you better. Basically it means to "make similar".
- Food is assimilated; when you eat it, it nourishes you and becomes part of you.
- In Star Trek, the species known as 'Borg' were assimilating other races -- taking the best parts and joining them into their system.
- Information can be assimilated -- it means to take in the information and thoroughly understand it.