Yes, “en avance” is a very frequent idiom of the French language. You can use “en avance” with the verbs ‘être’, ‘venir’, ‘aller’, ‘arriver’, and so on.

“Je suis en avance“, “Il est arrivé en avance“, “Elle est allée en avance à son rendez-vous“.

“En avance” means ‘earlier than a certain time reference’ which could be explicit or implicit. It is the opposite of “en retard”. It could mean something like ‘trop tôt’ or ‘plus tôt que prévu’.

Explicit: “Je suis arrivé en avance à la réunion” = I came earlier than the scheduled time for the meeting.

Implicit : “Je préfére venir en avance qu’en retard” = “Je préfère venir trop tôt que trop tard” = I prefer to come too early than too late.

You cannot use ‘tôt’ with the verb ‘être’, but you can do it with ‘venir’, ‘aller’, ‘arriver’, ‘partir’, and so on. So these are equivalent to the sentences above:

“Il est arrivé plus tôt que prévu“, “Elle est allée trop tôt à son rendez-vous“

En avance is the way to say “earlier than the expected time” in French. The opposite (later than the expected time) is en retard. This is different from tôt (opposite: tard), which means “early” in the sense of “near the beginning of some time period”. For example:

Je suis arrivé tôt à la gare, j’ai eu le premier train.
I came to the station early, I caught the first train.

Je suis arrivé en avance à la gare, j’ai attendu le train pendant une heure.
I came to the station early, I waited an hour for the train.

There are situations where both expressions work, e.g. “Je suis arrivé tôt à la réunion” or “Je suis arrivé en avance à la réunion” both mean “I arrived for the meeting more than a little before the starting time”. But in most cases they are not synonyms.

Avance in this meaning (it has others) is commonly found in the expression en avance, but it is also a noun which can be used outside of this set phrase.

J’ai terminé avec dix minutes d’avance.   I finished ten minutes early.
Le coureur en tête prend de l’avance sur le peloton.   The leading cyclist increases his lead over the pack.