spamming and phising
Spammers sent tons of messages everyday from all over the world. They are usually attempts to try and sell you things or try and get you to click on a link which will infect your computer. Most of the time they are easy to spot and you can delete them without doing any harm.
Phishing is a type of spam that tries to get you to reveal information. Its usually from your bank asking you to log in and 'verify' your password, except its not actually from your bank. Banks would never ask you for your details. So when you next get an email that is designed to make you panic just delete it as its probably just spam.