Zoho has restructured Zoho CRM's pricing and edition line-up more than once over the years, most recently as part of its "CRM for Everyone" changes. If your account has been running for a while, it's entirely possible you're on an older plan that no longer appears on Zoho's current pricing page.
In most cases, existing customers are grandfathered onto their existing plan rather than force-migrated onto a new one the moment pricing changes. Depending on when your account was set up, you may see your plan referred to by an older name, such as an "Old Standard" or "Old Professional" edition, and it may include a different mix of features and limits to the equivalent plan Zoho sells today.
Exactly what this means for your account, whether you'll eventually be asked to move to a current plan, what that would cost, and which features would change, depends on your specific subscription history and is not something that can be answered generically.
For Zoho's current published pricing and editions, see their Zoho CRM pricing page. This reflects what's on offer today and will not describe legacy plans that have since been retired.