In ultima online there are 3 stats: Strength / Intelligence / Dexterity. For short people call them: STR / INT / DEX.
Strength is related to your hitpoints, Intelligence is related to your mana and Dexterity is related to your stamina. You can view your stats by opening your character status-bar.

What is the statscap?

Each stat has an individual cap/max of 100 points but all 3 stats have a combined statcap of 225. So it is not possible to have 100 of strength, intelligence and dexterity at the same time.

How do I gain stats?

By gaining certain skillpoints, you have a % of chance to gain a relavent stat. Example: by gaining the snooping skill, you will notice gaining Dexterity too.

How do I lock/unlock them?

Open your character status-bar, here you can see your stats. Infront of each stat you see a golden lock. By clicking this lock your stat will unlock/lock.