This is a symbol of resurrection, innocence and peace.
Other factors can influence the meaning. An ascending dove represents the transport of the departed's soul to heaven. A dove descending represents a descent from heaven, assurance of a safe passage. A dove lying dead symbolizes a life cut prematurely short. If the dove is holding an olive branch, it symbolizes that the soul has reached divine peace in heaven.
note: excuse me for not having a better photo of a dove. Best I had in my archives, plus the person pasted away in 1877 so its fairly old.