Garden hose thread is a specific size and pitch that is not compatible with any other plumbing fittings. Its design facilitates a secure seal with hand tightening only, under most circumstances.
According the American National Standards Institute, garden hose thread--GHT--has an outside diameter of 1.0625 inches with 11.5 threads per inch.
Garden hose thread relies on a flexible washer to create a watertight seal, as opposed to pipe thread in which the taper of the thread and sealing compound applied to the thread create the seal.
Fittings that will adapt from pipe thread--NPT--to garden hose thread--GHT--can be found in any plumbing supply store or do-it-yourself home centre. They will be designated by the pipe size on the NPT side and simply GHT on the other. For example an adaptor with a 3/4-inch pipe thread on one end and garden hose thread on the other end would be identified as 3/4-inch NPT x GHT.
Garden hose thread has a history of minor leaks. These can usually be traced to missing, cracked or deformed washers, though faulty fittings contribute, too.
Garden hose repair fittings are widely available. In most cases the fittings completely replace the fittings currently on the hose and are held in place by hose clamps. It's always a good idea to attempt to fix a leaky garden hose fitting by installing a new washer before replacing the fittings.