Index finger pointing to the left.
It has no particular meaning and is mainly used to attract attention.
For example, it may be used near some?Link as a sign to follow it obligatory or to underline the extreme importance of some part of the message or post. Quite rare, it may also be used instead of the word "left" or "to the left" to indicate the position or direction.
Backhand Index Pointing Left was approved as part of Unicode 6.0 in 2010 under the name "White Left Pointing Backhand Index" and added to Emoji 1.0 in 2015.
U+1F448
? White left pointing backhand index