There are 650 parliamentary seats.
The parliament is 'hung' if there is no overall majority i.e. more than half of the seats, the smallest majority of two seats would be 326 (leaving the opposition with 324).
The bigger the majority, the better the chances of getting legislation and laws passed i.e. actually functioning as a government.
A government can be formed by parties allying together in the case of a hung parliament - for example if Labour had 250 seats and the lib Dems 100 and the conservatives 300. The largest party generally gets first dibs on forming a coalition government, but it could in theory be formed by all of the smaller parties banding together.
If a majority government cannot be formed, the queen may accept a minority government, usually once all other options are exhausted.
The problem UK parliament has had is that Brexit has divided people in their own parties, resulting in some MPs voting against their principles to align to their party, and some voting against their party to align with their principles. Typically MPs are willing to compromise to support the party line on less controversial matters so even a small majority is enough to function.
One of the current falsehoods is that a conservative majority will get Brexit done, I suspect there'll still be opposition from within the party, and unless they have a humongous majority (100+ seats) we'll continue dithering for months if not years.