Custom firmware it’s a firmware which is develop by android developers with addition of some sort of added features like tweaks, mods, changes etc.
Custom firmware it’s not an official firmware, your warranty will be avoid after flashing this.
You have to flash your smartphone with official firmware if you want to back on warranty.
Custom Recovery is a replacement of official recovery for Android devices
It Can Flash Custom firmware In Zip formats and it’s made by android developers.
It has many cool features that are not available in stock recovery.
It can take whole flash backup of your android device and can restore also if anything goes wrong in your Android device related to any software issue.
It can apply Tweaks, mods Ota Updates Also which is in Zip format.