`plan` returns resources where nothing is changed

Example:

  # aws_s3_bucket_replication_configuration.sw-xxx-ca will be updated in-place
  ~ resource "aws_s3_bucket_replication_configuration" "sw-xxx-ca" {
        id     = "sw.xxx.ca"
        # (2 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

  # aws_db_instance.postgres_v15 will be updated in-place
  ~ resource "aws_db_instance" "postgres_v15" {
        id                                    = "prd-postgres-v15-enc"
        name                                  = "userdb"
        tags                                  = {
            "workload-type" = "production"
        }
        # (55 unchanged attributes hidden)
    }

What does this mean? Thank you.