Yes, they are #(sharp), $(dollar), and %(percent).
You will notice that on a US keyboard, shift-4 is "$", which is the bash variable expansion character. On the keyboard, immediately to the left of "$" is "#". So, you can see that "#" is "at the beginning" of "$", and thus (according to our mnemonic), "#" removes characters from the beginning of the string. You may wonder how we remove characters from the end of the string. If you guessed that we use the character immediately to the right of "$" on the US keyboard ("%"), you're right!
So, #, which is before $, will remove characters from the beginning, and %, which is after $, will remove characters from the end of the string.
The bash is funny, easy while powerful. ;)
For more infomation about bash, click here.