I saw it on link to youtube, at 1:18 the following sentence:
Es schadet einem nicht
According to my understanding, "es schadet nicht" simply means "it doesn't hurt". But what is the meaning if "einem" is added? Does it mean: "it doesn't hurt, not even one"?
Perhaps you know man, as in: Man kann hier schwimmen / One/You can swim here. This is just a way to generically refer to unspecified people.
But man can only be used when it is the subject of a sentence (and hence only in the nominative case). However, for the accusative and the dative case, a replacement exists: the masculine form of einer (singular), i.e. einen in the accusative and einem in the dative case. (There is no alternative for the genitive case.)
This is what you are looking at here. Es schadet einem nicht simply means that it doesn't hurt one/you. An example with the accusative would be Ein Rechtsstreit kann einen viel Geld kosten (a court proceeding can cost you a lot of money).
Es schadet einem nicht.
It doesn't hurt one.
The verb schaden has a "built-in accusative object" corresponding to the noun der Schaden (damage). It goes with a dative object because of that. This einem is the receiver of the damage expressed by the verb schaden.
Rauchen schadet der Gesundheit
If it's clear from context, you can leave out the receiver.
Rauchen schadet.
Es schadet nicht.
This shows einem in the original sentence is put in to focus on the receiver one.
My answer differs slightly from the other two answers. In this context, I believe "einem" would mean "anyone."
So Es schadet einem nicht means, "It doesn't hurt anyone."
