Yes, if two miners find a block at the same time, this could cause a network split. one of these blocks is going to be orphaned, ( the one that is the slowest to have the next block build ontop of it usually).

The block that will be orphaned could have been seen as "valid/confirmed" by a number of services, but is now "deleted" (or rather not included in) from the main chain, with all the transactions that it confirmed.

See https://bitcoin.stackexchange.com/questions/5859/what-are-orphaned-and-stale-blocks for more information on orphaned blocks.