Both are different.
Kurla station operates only local trains -- Both harbour lines and central line local trains operate from here.
Lokmanya Tilak Terminus [LTT] operates long distance trains i.e. mail/express.
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LTT...
more... was earlier known as Kurla Terminus, bcoz it is situated in Kurla.
LTT is located in middle of two suburban railway stations, Tilak Nagar and Kurla, on the Harbour Line.
Central Railway decided to expand LTT to take on more rail traffic, as the Chhatrapati Shivaji Terminus [CST] was unable to handle any more express trains.