Direct charging means that the plug is directly connected to the phone, and you can make a call while charging. For example, when you use the phone suddenly no power, and there is no spare battery, at this time you need to use direct charging - charging is to take out the battery and put it on the charger. If it is the original phone, the charging effect is the same. Some universal chargers take a long time to charge. Depending on how you like it.
If you have two batteries, a charger is fine.
Of course, the best is to have a charge of two