Odoo is an integrated business system covering CRM, inventory, invoicing, HR, project management, e-commerce, and website in a single platform. It sounds too good to be true. Partly because it is, partly because it actually holds up.
Strengths
Everything in one system. Sell a product through the online store and it automatically creates a delivery order in the warehouse, an invoice in accounting, and an entry in CRM. No integration to maintain, no sync issues between separate systems. That alone saves hundreds of hours per year for mid-sized companies.
Community Edition (CE) is open source and free. Run it on your own server, own your data, and pay nothing in license fees. Enterprise costs money, but CE covers most basic needs.
Limitations
Documentation is uneven. Some modules have excellent documentation, others have almost none. The community forum is active but answers can be contradictory since versions differ significantly.
Upgrades between major versions (16 to 17, 17 to 18) are not trivial. Database migrations often require manual work, and community modules that aren't actively maintained can stop working.
Community vs Enterprise
Enterprise adds: Odoo Studio (visual customization), MRP (manufacturing), field service, mobile signatures, and official support. CE lacks these, but has an active community building alternatives. The choice depends on budget and requirements.
Odoo fits best for companies that want one system instead of ten. If you already have established systems that work, the migration effort is rarely worth it. But starting from scratch, or replacing a patchwork of systems, Odoo is hard to beat.