Changes

Reboots your device. This is the standard reset that's also accessible when you press the power button.

Only Soft reboot, also refered to as quick reboot, only reboots the AndroidOS instead of performing a complete power on reset.

Reboots your device into recovery mode. If you have a custom recovery like TWRP installed, you can use recovery mode for flashing new ROMs or creating/restoring backups.

Reboots your device into bootloader (fastboot mdoemode). This option my be locked on some devices. Usually, you can unlock fastboot mode in developer settings.To enable developer settings on your phone, go to ''Settings > About phone'', look for section ''Build Number'' and tap it 7 times.

To enable developer settings The fastboot protocol is used in combination with the fastboot tool on a PC to directly flash partitions on your phonedevice's flash memory.It can flash recovery or boot (kernel) images, go the splash screen image or complete firmware updates.  Nowadays, most devices come with a locked bootloader and you need to //Settings > About phone//unlock your bootloader first, look for section //Build Number// and tap it 7 times.