An ETA allows you to travel to the UK to visit for up to 6 months. Whether you can apply depends on the date you travel and your nationality as shown on your passport.
Nationalities from the following locations (including associated territories) can apply for an ETA now
You do not need an ETA if any of these apply to you:
A Traveller's passport should be valid for a minimum period of 6 months from the date of entry into the UK.
With an ETA you cannot:
The ETA fee is 50 GBP(Single Entry) including mandatory government fees and statutory fees.