You can apply to vote by post for a particular election, for a set period of time or for all future elections. However, you must be registered to vote first. Postal votes can be sent out to addresses in the UK and abroad. If you fill in a postal vote application form, you will be unable to vote in person at a polling station.
A proxy vote is when you have arranged for someone to vote on your behalf, in your absence. Any elector can request a proxy vote for a particular election as long as they give a reason.
If you have a proxy vote this means you can still vote in person at your polling station provided you vote before your proxy.