Once you have made an assignment such as x=2, then whenever x is evaluated, it is replaced by 2. Sometimes, however, you may want to continue to refer to x itself, without immediately getting the value of x.
You can do this by referring to x by name. The name of the symbol x is the string "x", and even though x itself may be replaced by a value, the string "x" will always stay the same.
The names of the symbols x and xp are the strings "x" and "xp".
remove completely all symbols in the Global` context
Removing all symbols you have introduced.
If you do not set up any additional contexts, then all the symbols that you introduce in a Wolfram Language session will be placed in the Global` context. You can remove these symbols completely using Remove["Global`*"]. Built‐in Wolfram Language objects are in the System` context, and are thus unaffected by this.