Sometimes, I've seen Checkbox but I've also seen Tick Box. Does anyone know what's going on?
It's all the same. The reason is the language difference of each spreadsheet.
A checkbox (check box, tickbox, tick box) is a GUI widget that permits the user to make a binary choice, i.e. a choice between one of two possible mutually exclusive options.
In Japanese it looks like this:
You can switch to any language here:
Google offers several English variants, like English (United States), English (United Kingdom), etc., for their apps UI. Some UI elements names are exactly the same but others aren't like occurs on this case.
Another case is the Gmail, on English (United States) there is a
Trash while in English (United Kingdom) there is a
Bin but both shows the deleted email messages.
The instructions to change the Google account language are on Change language. Once you select English, pay attention to the next dialog as it list all the English variants that Google offers for the Google apps UI.
NOTE: The setting that you choose applies to all the Google apps UIs, there isn't a way to set the language to be used on an app by app way, but some apps like Google Sheets could have a setting for certain features like the language to be used for Google Sheets functions.