In Dungeons and Draogns 5e the Armor class is a metric that measures the degree in which a character is able to defend himself/herself from incoming attacks.
How can you calculate the Armor Class in D&D 5e?
In general, you can use the following formula to determine this value. Keep in mind that it is not always guaranteed that you can have access to all these possibilities to increase it.
10 + DEX Modifier + Shield + Magic Items + Abilities from Class/Race
or, if you decide to wear armor…
10 + ARMOR + DEX Modifier (within the limits) + Shield + Magic Items + Abilities from Class/Race