What you are actually practicing
Three of the four words belong to the same group and one breaks it. The task looks like vocabulary, but the skill is categorisation: deciding what kind of thing each word names, and finding the odd one by structure rather than by feel.
It is the same move used in sorting data, reading a table, or noticing that one number in a list is not like the others.
How the game works
You are shown four words and asked which does not belong. Pick it; a wrong pick reveals the answer immediately.
Easy uses broad everyday groups — animals, colours, foods. Medium widens the set. Hard uses categories that are closer together, where a shared property can mislead.
The groups worth recognising
Animals, foods, vehicles, furniture, clothing, body parts, tools, stationery, instruments, jobs, seasons, days, months, cities, planets, shapes, feelings.
Strategies that actually raise your score
Find the group of three, not the odd one. Naming the category the majority belongs to is faster and more reliable than testing each word against the others. Once the three are named, the fourth is the answer by elimination.
Check word class before meaning. If three are nouns and one is a verb, that is enough — you do not need to know what they mean.
Beware the shared property. A lemon and a ball are both round, but that does not make them the same kind of thing. Ask what the word is, not what it looks like.
Test the category out loud. Say "these three are all ___". If the blank will not take a single common word, you have grouped them by accident and should look again.