He had encountered a lot of prejudice.
What is the meaning of this sentence?
Probably, a lot of people were against him due to his skin color or old age.
I have seen people dislike all those who are over 50.
Some people dislike non-white people.
Prejudice can take a lot of forms. It doesn't have to be about colour or age. The context of the rest of the piece should tell you what kind of prejudice he had encountered.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.