If you've installed a lot of apps on your iPad, they could be eating up a large amount of your iPad's limited storage. Games are one of the biggest offenders, with titles like Infinity Blade, Asphalt, Rage HD, and many others taking 1 GB each or more. Removing games and other apps that you don't use anymore can free up a lot more space than you may think.  While you can delete apps from your Home screen fairly easily, this method will sort your installed apps by their size and allow you to see how much space each app is taking up. Don't worry about losing access to the apps you uninstall. All of your downloads are stored with your Apple ID, and you can redownload any app, free or purchased, from the App Store at any time. If you want to back up an app, you can use iTunes to copy all of the documents and data associated with the app before deleting it. If you have iCloud Backup enabled, app data will be automatically backed up when your device is backed up to your iCloud storage.   This may take a few moments. You will see how much space the data associated with the app is taking up. Tap "Delete App" again to confirm that you want to delete the app and all of its associated documents and data. You can potentially free up a lot of space by regularly cleaning out your apps.

TL;DR in Chinese:
理解为什么要卸载不用的软件？如果iPad上装了很多App，它们会占用很多的空间。 打开设置，选择“通用”。 点击“储存空间与iCloud用量”。 等待应用列表读取完毕。 点击不再使用的应用，可以看到其占用的空间量。 点击“卸载应用”，确认你要删除应用及其相关的所有文件和数据。 对所有不用的应用重复以上步骤，来清理程序。