Just a correction to the above responses. # = 'pound', 'number', 'hash', or 'sharp' symbol. When you are pronouncing this symbol as a sequence of letters or numbers then you pronounce it as 'pound'. For example, #AER23 = 'pound', A, E, R, 'Two', 'Three'. When its used to define something as a number and not a sequence of something then you pronounce it as 'number'. For example, #4 = 'Number 4'. Here it is called the 'number' symbol. The '#' symbol can be prefixed to other words or phrases to form a metadata tag known as a hashtag. This is primarily used only in microblogging social networking, and it commonly known as the 'hash' symbol. When reading music, # is known as the 'sharp' symbol. For an exmaple, C# = C 'Sharp'. C# (C 'Sharp') is also a computer science language. People will often pronounce the symbol in many different ways even when saying words, letters, and symbols in sequence. As long as you pronounce it with one of the 4 mentioned above you should not be wrong. People may or may not notice but they will still understand you. It makes you appear more intelligent when you pronounce it correctly.

I did customer service over the phone years ago. Those characters are hard to describe to people over the phone. We call them: / > forward slash # > pound sign * > star (or asterisk)

/ = forward slash # = hashtag * = asterisk (Greek for little star) & = ampersand : = colon ; = semicolon \ = backslash I hope that answers your question :). If you want to know the names for more of those symbols read Michael's comment.

逗号：comma；句号：period；星号：asterisk；斜杠：slash #号number sign美式英语里也称之为pound sign或者pound key，但在英式英语里pound sign的说法是专指英镑（pound）符号“£”的。 在英国和澳大利亚，还会将#称为hash，或者hash key、hash mark。

/ = forward slash # hash ^ carrot ! exclamation @ at $ dollar % percent & ampersand * star ( left paranthesis ) right paranthesis + plus - minus _ underscore : colon ; semicolon ? question mark \ back slash