Do I need to tag ports connected 2 switches?

Hey guys, i'm super confused with the HP VLAN terminology and inner working.

I have 2 switches, us1-sw02 and us1-sw05.

sw02 has 5 vlans, 1, 20, 69, 100, 101

sw05 has one vlan 1

Both switches has vlan 1 as default vlan. There is no management vlan, my predecessor made it that way.

Anyway, this is insanely confusing to me. So sw02 is the core switch cause it has all the servers hooked into it. The only empty port is 14.

sw05 is just a temporary switch I found on the shelf.

So I connected port 14 on sw02 to port 48 on sw05 and so far both switches are talking to each other. I didn't create a trunk or tag anything on any switches.

From sw05, when I connected to say port 1 using my laptop, I could receive an IP and be able to access the entire network.

How is this possible? Is it because both switches are forwarding all traffic through the Default_VLAN?

Do I need to create a new VLAN for my purpose on sw005 and tag port 48 and also port 14 on sw02?

Any help is appreciated. Thanks.