This is the 218th most frequent German word.
erhalten
To receive, obtain, or preserve.
In this sentence, 'erhalten' is used in the sense of 'to receive', referring to obtaining the letter.
Ich habe gestern einen Brief erhalten.
I received a letter yesterday.
Here, 'erhalten' indicates the state of being preserved or maintained in good condition.
Dieses Gemälde ist gut erhalten geblieben.
This painting has remained well-preserved.
In this context, 'erhalten' implies gaining or receiving something abstract, such as recognition or approval.