I lent John $5 yesterday = John borrowed $5 from me yesterday.

Think about the difference between 'take' and 'give'. That's clear, isn't it? Well, the difference between 'borrow' and 'lend' is exactly the same as between 'take' and 'give'. If I lend you something, I 'give' it to you for a short time. I I borrow something from you, I 'take' it from you for a short time. It's really that simple.

I go to the library for books every month. I don't buy the books, but I take them home to read. Two weeks later I return the books to the library. I borrow books, the library lends books.