When a toilet constantly seeps water out of the tank into the toilet bowl that cause is by the toilet flapper inside the tank which is made of rubber.
Sometimes those chains either plastic or metal that attach to the toilet flush handle and to the flapper become kinked a little not allowing the flapper to fully close and seal off the water in the tank to the toilet bowl.
Sometimes just fixing the chain will stop the water leaking into the toilet bowl but if not replace the toilet tank flapper which is really cheap and easy to replace.
Take the old one off and go to Lowes, Home Depot or other hardware stores and get an exact replacement then just pop the other one on and then reattach the chain to the flapper and handle and make sure it's closing properly.