Actually, bootloop is just the most easy situation to handle on your Android device if you make a fail modification or hack on it. There are his big brother which worse called "soft brick" and "hard brick". And this is the difference between them:
Bootloop on Android
The name said it all, a looping on booting process. Bootloop is happen if you make a fail modification or hack to your Android device, and after you restart your Android device it is just give you a boot animation on the screen forever.
You know boot animation right? Boot animation is like the gif image you see when you waiting for your Android device to live and enter homescreen. Example boot animation on Samsung Android device is the Samsung logo with white dot splash animation. Boot animation on CyanogenMod ROM is Cyanogen alien face with animation of white circle around it.
The boot animation process is usually take 1 to 5 minutes. But in bootloop state, it will take forever. Even if you waiting 1 hour, 3 hour, your device won't start.
Usually if you make a modification by flashing a zip file through recovery and the result is gave you a bootloop, it can be fixed by also flashing the uninstaller zip file provided by the mod author's to remove the modification from the device system. Example from the Xposed installation on Android Lollipop and up, it require us to install a zip file through the recovery and if the result is gave us a bootloop, to fix it just simply flash the uninstaller zip file which the developer provided
To fix bootloop is just simply restore from your Android device nandroid backup or flashing some uninstaller zip file where the mod authors provided.
Soft Brick on Android
Softbrick on Android is a state where the device even not enter boot animation. The device just pass untill boot logo and then it will like that forever.
Different with boot animation, bootlogo is the static image of the Android device manufacturer logo and usually followed by text at the bottom "Powered by Android". Bootlogo is the first state ever your device will shown on the screen in the booting process. It give you sign that the device is still fixable by yourself if you make a fail modification. The ordered process of device booting is: Boot logo -> Boot animation -> Device live and enter homescreen.
To fix soft brick on your Android device is just simply restore from your nandroid backup. If that's not helped, you need to reinstall the firmware of your Android device with the stock firmware.
Hard Brick on Android
Hard Brick is the worst situation ever happen to your Android device if you make a fail modification / hack where the device is totally dead. It even not showing you the boot logo, the screen is just totally black.
Well, if your Android device got a hard brick don't desperate first. Try to restore from the nandroid backup, and if that not helped try to reinstall the firmware, and if that's not helped too maybe you should take your Android device to the service center or the repairman :D
Best practice when make a modification on an Android device to prepare the possibilities of bootloop, soft brick, or hard brick
If you are going to make modification on your Android device moreover it is a big modification like installing a custom ROM, it is very recommended to make a nandroid backup first.
Nandroid backup is like a snapshot of your Android device which containing whole device content, system, and even installed applications. The nandroid backup is made using custom recovery like CWM, TWRP, etc. So, if something wrong happen to your Android device after did some modification, simply just restore it back from the Nandroid backup you made. Nandroid backup is already save my Android smartphone from bad situations many times i couldn't remember.
Good reader make a good comment! If there is a mistake or broken link, please add a comment...