The words pore, pour sound the same but have different meanings and spellings. Why do pore, pour sound the same even though they are completely different words?
The answer is simple: pore, pour are homophones of the English language.
To read or study carefully and attentively: pored over the classified ads in search of a new job.
To gaze intently; stare.
To meditate deeply; ponder: pored on the matter.
A minute opening in tissue, as in the skin of an animal, serving as an outlet for perspiration, or in a plant leaf or stem, serving as a means of absorption and transpiration.
To make (a liquid or granular solid) stream or flow, as from a container.
To send forth, produce, express, or utter copiously, as if in a stream or flood: poured money into the project; poured out my inner thoughts.
To stream or flow continuously or profusely.
To rain hard or heavily.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").