Daylight Saving Time is the name given to the process of setting clocks forward by an hour during spring and summer, then setting them back again during Autumn and Winter. The benefits of this biannual ritual are largely to do with making the most of natural daylight. The history and politics though, are for more controversial.
In the US, Canada, and parts of Mexico, DST already began on Sunday, March 8, 2020. In the UK we switch from Greenwich Mean Time (GMT) over to British Summer Time (BST) on Sunday 29th March. Not all European countries observe DST, but those that do will also switch over at the same time.
All of these switches happen simultaneously, irrespective of local time or timezone. So countries on Western European Time (UK, Portugal) will switch at 1am local time (to 2am local time) whilst countries on Central European Time (France, Germany etc) will switch at 2am local time (to 3am local time) etc.
If you live in Europe then this may one of the last few times you have to deal with this seasonal change. Last year the European Parliament voted to permanently stop observing DST. If this becomes law then next year will be the last time DST is observed in Europe.