TRIM is a subset of the ATA commands specific to SSDs.
Can you operate without it? Sure, but it will treat your SSD as if it were a spinning HDD - impacting performance and lifespan.
The TRIM command enables an operating system to notify the SSD of
pages which no longer contain valid data. For a file deletion
operation, the operating system will mark the files sectors as free
for new data, then send a TRIM command to the SSD. After trimming, the
SSD will not preserve any contents of the block when writing new data
to a page of flash memory, resulting in less write amplification
(fewer writes), higher write throughput (no need for a
read-erase-modify sequence), thus increasing drive life.
If your MacBook Pro came with an SSD, it's enabled by default. If not, you must enable TRIM when you upgrade to an SSD.