You use that 12-24 word seed as a backup. Let's say, if you lose access to your computer, you grab your new computer(or phone), install a reputable(and open source) wallet app, enter in the 12-24 words, then boom shakalaka. You now have access to your funds.

With that said, I hope you don't have funds on that wallet backup on your screenshot. Treat your wallet seed like how you treat your finance/online banking account passwords and backup codes. Giving people access to your seed will give them access to your funds.

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EDIT: apparently the screenshot is from blockspoint.com.