The '100 Watts' quoted in that listing is an indication of the maximum power rating that its components are designed to handle. The actual light output would depend upon the type of bulb that you put into it, which could be any bulb with a BC (bayonet cap) fitting. In practice, using any modern low energy bulb, you shouldn't need to use anything like 100W to achieve a decent light level.
When most of us around here were youngsters, standard (incandescent) light bulbs were rated by their wattage but these days, with so many different types of bulbs available, they're rated in lumens. This table can help you to convert:
https://www.thelightbulb.co.uk/wp-content/uploads/2015/08/led-lumens-to-watts-conversion-chart.png
Going back to 'the good old days', most people will have probably used 25W or 40W bulbs in their desk lamps. If that's the level of light output that you now want to achieve from more modern bulbs, look down the first two columns in the table to see the power rating of the newer types of bulbs.
In the same 'good old days', most people might well have chosen to use a 60W bulb in a bedroom but a 100W bulb in a living room or kitchen. To find the power ratings of more modern types of bulbs, look down the third or fifth columns respectively. (In all cases though, pay particular attention to the column
headings, as its 'lumens' that you really need to be looking for, rather than 'watts', these days.
So, if you only want enough light to find your keys by, look for a bulb providing perhaps 300 lumens of light. However if you want a really bright light, look for a bulb providing around 1500 lumens. As you'll see from the chart, all modern bulbs providing such outputs use under 100W, so the lamp you've linked to is fully compatible with any of them.
For specific examples, I'll suggest this as a possibility for a really bright light:
https://www.diy.com/departments/diall-b22-15w-1521lm-gls-warm-white-led-light-bulb/3663602667551_BQ.prd
and this for a bulb that, although not really bright, will easily give you enough light to find your keys by:
https://www.diy.com/departments/diall-b22-3w-250lm-mini-globe-warm-white-led-light-bulb/3663602667810_BQ.prd
At 15W and 3W, respectively, they're both well within the 100W maximum limit of the lamp. (If you could actually buy a 100W halogen bulb, you could probably light Trafalgar Square with it!).