This is the 1053rd most frequent Spanish word.
experto
A person skilled or knowledgeable in a particular field.
In this sentence, 'experto' is used as a noun to denote a person skilled or highly knowledgeable in a particular field.
Él es un experto en matemáticas.
He is an expert in mathematics.
Here, 'experta' is used as an adjective, modifying 'manera' to describe the manner as being skillful or done with expertise.
Ella completó el trabajo de manera experta.
She completed the work in an expert manner.
'Experta' is again used as an adjective, this time modifying 'capacidad' to specify that the capability required is of expert level.