Wifi signal booster or router modem? Which device should I buy?

There are devices that allow it to distribute the internet received wirelessly, for example, the wifi we receive remotely is very little in our house and it does not work everywhere in our house, for this there are router modems or wifi multiplier devices.
Do you use such a device, which do you think is better?
wifi signal booster
router modem
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Wifi signal booster or router modem? Which device should I buy?
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