I assume that there is difference between the commands Clear and Remove. But it seems to me that I am not aware of any caveats against their misuse. For instance,
a = 5; a =.; ?a. (* or *) a = 5; Clear[a]; ?a.*
a = 5; Remove[a]; ?a.
The effects are the same and so is the error message:
Information::nomatch: "No symbol matching a. found."
Another curiosity is about the warning difference if a dot is omitted after a,
a = 5; Remove[a]; ?a
Information::notfound: "Symbol a not found. "
To see the the difference, try:
a = 1;
f[i_] := a + i
f[1]
2
Clear[a]
f[1]
NameQ["a"]
1 + a
True
Remove[a]
f[1]
NameQ["a"]
1 + Removed["a"]
False
As you can see, Remove has a different effect on other definitions that a is inside of. After Removing, a is not allowed to be used anymore because it doesn't exist anymore, even symbolically. You have to recreate a and any function depending on it, because even if you recreate a, f will still be in a broken state:
a = 1;
f[1]
1 + Removed["a"]
Remove is often overkill, but it's sometimes necessary if you need strict control over which symbols exist and which ones don't. And as Goofy remarks in a comment: Remove also deletes the symbol from the auto completion functionality in the FrontEnd, which can be useful to be aware of.
In short summary:
Clear deletes most "normal" definitions associated with a symbol, but not Options and Attributes etc.ClearAll deletes everything associated with a symbol, including Options and Attributes (and some other stuff). In normal everyday use of WL, you'll hardly ever need a bigger cannon than ClearAll.Remove deletes the entire existence of a symbol itself.