Lend = to GIVE something to someone for a time. Borrow = to TAKE something from someone for a time For example, if I don't have any money... ...my friend can LEND some money TO me. ...I can BORROW some money FROM my friend.

Adding to Su.Ki.'s answer, there is a usage point that you will run into sooner or later. Let's suppose I am giving you $100 with the expectation that you will pay it back. 1) You are borrowing $100 from me. (The verb is "to borrow.") 2) I am lending you $100. (The verb is "to lend.") 3) The $100 is a loan. I am making you a loan of $100. (The noun is "a loan.") 4) Afterwords, I have lent you $100. (The past tense of "lend" is "lent.") And now, here is the usage point people argue about. Everybody agrees that it is correct to say "I am lending you $100." However, native English speakers frequently take the noun form, "loan," and use it as a verb, "to loan:" "I am loaning you $100." "He loaned me $100." Some people feel that "to loan" is just plain wrong, not acceptable, and "bad English," so don't use it yourself. Other authorities feel that it IS acceptable. I see that the American Heritage dictionary makes the interesting point that when "to loan" is used, it always refer to something physical: I can lend you money, I can "lend a hand" (help), I can loan you money, but I can't "loan a hand." As a foreign speaker, understand that "to lend" and "to loan" mean the same thing, but always use the "lend" form yourself.

When you give something, you lend it; when you get or receive something, you borrow it. In understanding that both will be returned after a short period of time. Thus you say, "Can I please borrow your book?" and "Do you want me to lend you my book?"

Hi Talita! "Lend" is like "emprestar" --> to give something to someone and expect it back --> Can you lend me your pen, please? I will give it back to you just now. "Borrow" is like "tomar emprestado" --> to take something from someone who expects it back --> I borrowed his pen and I forgot to give it back to him... I hope it helps :-)

Re-posting my comment as an answer.