Help needed with PF ruleset

[spaghetti_bolognese]

I'm learning PF firewall for now and I'm looking at OpenBSD's page on PF.

I'm looking at the example and there's this line that I don't quite understand.

pass in on egress inet proto tcp from any to (egress) \
    port $tcp_services

I'm not sure if I understand this correctly, but I think that the bolded part meant that this rule will allow any TCP protocol traffic from egress (external outgoing interface) from any source. However, I don't get the subsequent part.

(egress) \
    port $tcp_services

Could someone please explain it to me?

Kind regards and thanks in advance.