Why Is Mining Important?
Bitcoin mining is an essential aspect of the security of Bitcoin's network. In order to remain independent of a third part, Bitcoin needs to prevent funds from being spent more than once. This is resolved by using digital signatures to identify authorized users, who hold a private-public key pair that only they can use to spend or move Bitcoins.
There is still the threat of the "double-spend problem", where Bitcoins have already been spent, but either an authorized user or an unauthorized one are trying to spend that Bitcoin again. Mining helps prevent this issue with hash-based proof of work.
Proof of work orders transactions into blocks that the network verifies by looking at the longest chain of blocks. This procedure makes it incredibly difficult for someone to "reverse" a transaction and attempt to re-spend Bitcoins.
Without Bitcoin mining, Bitcoin itself would become an incredibly disruptive cryptocurrency due to repeated misuse and lack of monitoring.