What is as?

It seems like your request might be incomplete or unclear. "As" could refer to various topics, including but not limited to:

1. "As" in English Grammar: It is a conjunction or preposition used to indicate a comparison, role, or function. For example, "as fast as," "as a teacher," or "as I said."

2. AS (Aortic Stenosis): A medical condition where the aortic valve becomes narrowed, affecting blood flow from the heart to the aorta and beyond.

3. "As" in Unicode/ASCII: It could refer to the ASCII code of certain characters (for instance, ASCII value 65 represents 'A' and 83 represents 'S').

4. "As" in Music: The key of A♯ (A sharp) is sometimes informally referred to as "as," especially in certain languages.

5. AS (Autonomous System): In computer networking, an Autonomous System is a collection of IP networks and routers under the control of one entity that presents a common routing policy to the Internet.

6. AS (A/S for Aktieselskab): In some countries, like Denmark and Norway, "A/S" is used to denote a stock-based company, similar to "Inc." or "Ltd."

If you had something specific in mind, please provide more details, and I would be happy to offer more targeted information!