Within your easy access pot is an ISA, which is a tax-free savings account, meaning you won’t pay any tax on the money you make within it (which can be a huge saving over time).
You can save up to £20,000 per tax year (April 6th to April 5th the following year).
If this limit is reached, or you don’t want to save within an ISA, a standard account will be used (this doesn’t have any tax-free benefits).
You can access money within a few days but could be around a week. Investments must be sold first, which takes time and only occurs on weekdays.
Note: the government could change these tax or any other rules in the future, and your overall tax treatment will depend on your individual circumstances.