Minimal pairs are used as pronunciation practice; the meaning of the word is not really important in this regard.
For example, these are minimal pairs:
bus - but
haul - hole
baking - making
Minimal pairs are useful in the classroom when you are looking at the pronunciation of certain words and sounds. They are used to isolate the single sound differences so that your students can concentrate on the problem area without getting distracted by other noise.
Say, for example, you are teaching the difference between /ɪ/ and /iː/ you could use words like:
find - bleating
However, here the student has to contend with several different sound differences between the two words. It is far better to use two words whose only difference is /ɪ/ and /iː/ such as:
ship - sheep
Of course problems with pronunciation vary with the student's mother tongue. Japanese students, for example, have problems with /f/ and /h/ (because Japanese does not have the /f/ sound) so a minimal pair like
fat - hat
is useful in this case. Likewise, Greek students have difficulty with
show - so
because Greek does not have the /ʃ/ sound.
Yes. Why? Partly because some students are not able to hear the difference between two words which may - to them - sound exactly the same but which may have completely different meanings.
Look at these two sentences:
Who will chair the conference?
Who will cheer the conference?
A student may think they have understood the sentence, but in fact they could easily come away with the wrong impression of what was said.
Here's a simple game you can use to practice minimal pairs with your class. You can adapt and extend it to make it suitable to the level of your class.
Firstly, make a note of the sounds which your students have problems distinguishing between. Then make a list of minimal pairs which cover those sounds. For each word in the list, make 3 flashcards and print the word on it.
In the classroom, shuffle the cards and deal them out to all the students - make sure they don't show anyone else what cards they have. Get the students to stand up and mingle. They need to go around the class trying to collect pairs, asking other students, "Do you have a sheep?" for example.
If the other student does, they must hand it over. If not, they move on.
The game continues until all the cards are made into pairs.
See also Pronunciation Snake - a pronunciation game with minimal pairs.
Not all of these will apply to your class but they can give you a good idea of what minimal pairs are all about and examples of what you can use.