A ship is an oceangoing craft ( boats are for lakes and rivers ). The two main types are power and sail.
Powered ships include tankers, freighters, cruise ships, whalers, etc.
Sailing ships are a bit more complex, they can be classified by what they do, similar to the powered vessels, but also by the number and location of the masts and sails. The difference between ketches, yawls, schooners, sloops, and such, fall into this category.
Some ships just refer to a style of use ( fishing, yachts, etc. ) and can be either type.