UK politics is a complex beast, consisting for four countries (England, Wales, Scotland and Northern Island) in a United Kingdom. Three of the four have their own representation, England does not (at this time). Elections to the UK parliament are held using a voting system called 'First Past the Post'. This is where the country is divided into regions called constituencies.
Whoever gets the most votes (not a majority) in a constituency is elected as a Member of Parliament.
If one political party has more MPs than any other, then that party forms a government, and takes over Number 10 Downing Street.
If no party has an overall majority, then a coalition can be formed.