I took an English assessment test online and this was my answer:
Someone suggested to go for a walk.
My answer was wrong and this was the correct sentence:
Someone suggested going for a walk.
Can someone please explain why my answer was wrong?
A suggestion (what is suggested, the object of the verb suggest) is a noun. You can't use an infinitive verb where a noun is required.
Going here is a gerund, a form of the verb go which functions as a noun.
[Note that suggested can followed by that and a finite verb, "suggested that we go". That's different; that is a conjunction introducing a clause expressing purpose, end, aim, or desire.]
I never find much difference in use of infinitive and gerund. However, it is always suggested that few verbs are always followed by gerund whereas few are followed by infinitives only.
I found a good distinction somewhere over the Internet which may help
Often we use the gerund for an action that happens before or at the same time as the action of the main verb.
In your example:
He suggested for a walk at the same time to be happened not sometime in future.
However someone may suggest for future action too;
So I personally don't consider that sentence as wrong sentence.
From the other resource, I found;
There are few verbs which wants second action to be happened with main action; Eg
These verbs are always followed by gerund.
'Someone suggested TO GO for a walk' implies that you are going somewhere for your walk. 'Someone suggested GOING for a walk' implies just the act of walking itself, without inference to any location to take the walk.