International character map in Linux?

Is there any way to find a ‘character map’ in Linux. The following shows instructions for Windows, is there a Linux equivalent that I can use?

To access additional characters when indexing:
Click the Windows Start button.
Select Programs.
Select Accessories.
Select System Tools.
Select Character Map.
With the Character Map open, click the desired character. Drag the selected character, which is enlarged on the screen into the indexing field and drop into the name being indexed. If the character is going to be used multiple times, drag the letter into the “Characters to copy” field at the bottom of the Character Map and click “Copy,” then Paste (Ctrl+V) while indexing to insert the character each time the character appears. Another method is to click the character, click Select and then Copy. Return to the indexing program and click Paste (Ctrl+V) into the word being indexed. More character options can be found by changing the font at the top of the Character Map.

Which Linux distro are you using ?

You mean like this:
https://help.ubuntu.com/community/CharacterMap