The questions nobody wants to ask out loud

An MP represents one constituency in the House of Commons. They vote on national laws and budgets, can question ministers, sit on committees that examine policy, and take up constituents' problems with government bodies. They do not run local services, and they cannot overturn a council's planning decision.

A councillor is one of several elected to run a council. Together they set the council's budget and council tax, decide planning applications, and oversee services: bins, streets, parks, libraries, housing and, in county and unitary councils, social care. They have no power over the NHS, income tax or immigration.

A party's published programme for an election, setting out what it says it would do if it won. There is no legal obligation to deliver it. Manifestos are the main published source for party positions, which is why so much of this site quotes them.

The voting system used for UK Parliament and most English council elections. You mark one cross; the candidate with the most votes wins, even if most people voted for someone else. It tends to favour parties whose support is concentrated in particular places.

A family of voting systems that try to make seats match votes more closely. Scotland's councils and the Scottish Parliament, the Senedd and Northern Ireland use forms of it; Westminster does not.

A seat won last time by a small margin, so a modest change in votes could change the result. It is a description of the past, not a prediction: boundaries change, candidates change, and people change their minds.

Broad labels, not exact ones. Roughly: the left tends to favour more state action to reduce economic inequality; the right tends to favour lower taxes, smaller government and market solutions. Many important questions — Europe, immigration, civil liberties, the environment — cut across the line, and parties contain a range of views.

An election for a single seat between scheduled elections, usually because the sitting member has died, resigned or been disqualified. Turnout is usually lower than at a general election.

Yes, but you need to sort it out in advance: apply free for a Voter Authority Certificate, or use a postal vote, which needs no ID. Photo ID is required at UK Parliament elections and English council elections, not at Scottish or Welsh council elections.

It is counted by hand, in public, with candidates' agents watching. A paper that is unclear or marked for too many candidates is set aside as spoilt, and spoilt papers are counted and reported. Your paper has a number, but the law protects the secrecy of your vote.

Council by-elections are frequently decided by tens of votes, and the ward result on this site's Lambeth pages was decided by 88. We cannot tell you your vote will decide the result; we can tell you that small margins are common and that non-voting is itself counted and noticed by parties.