An avenue is a street, especially a wide one lined with trees. An avenue is also any approach to doing something. For example, this web site might be a new avenue you have found for learning words.
The word avenue comes from the French avenir, meaning "to come to, or arrive." The first meaning is simply a wide street. An avenue — or boulevard — is likely to be busy, unlike a quiet side street. The abbreviation is ave., as in Park Ave. Also, an avenue is a way to accomplish something. If you need money but can't get a loan, you'll have to find another avenue.