UK Parliament elections and most council elections in England use first past the post: one cross, and whoever gets the most votes wins. They don’t need more than half. Try it with four make-believe candidates.
310 (31%)
280 (28%)
240 (24%)
170 (17%)
Candidate A wins with 310 of 1,000 votes (31%). More people (690, or 69%) voted for someone else, but that doesn’t change the result.
The candidates here are invented and stand for no party. Scottish and Northern Irish council elections, the Scottish Parliament and the Senedd use other systems; your ballot page says which one applies. Source: Electoral Commission.