> For the complete documentation index, see [llms.txt](https://docs.emsigner.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.emsigner.com/key-concepts.md).

# Key Concepts

- [Users](https://docs.emsigner.com/key-concepts/users.md): Different user roles that shape how documents are sent, signed, and managed.
- [Departments](https://docs.emsigner.com/key-concepts/departments.md)
- [Envelopes](https://docs.emsigner.com/key-concepts/envelopes.md): Bundle multiple documents into one secure package for easy sending and tracking.
- [Signature Fields](https://docs.emsigner.com/key-concepts/signature-fields.md)
- [Workflows](https://docs.emsigner.com/key-concepts/workflows.md): Defines the order and method in which recipients act on documents.
- [Templates](https://docs.emsigner.com/key-concepts/templates.md): Reusable document formats that save time and ensure compliance across teams.
- [Electronic and Digital Signatures](https://docs.emsigner.com/key-concepts/electronic-and-digital-signatures.md): Two ways to sign: simple intent-based methods or cryptographically secure signatures.
- [Types of Electronic or Digital Signatures](https://docs.emsigner.com/key-concepts/electronic-and-digital-signatures/types-of-electronic-or-digital-signatures.md): Three signature levels—SES, AES, QES—each offering different trust and security.
- [Electronic Seals](https://docs.emsigner.com/key-concepts/electronic-seals.md)
- [Timestamping](https://docs.emsigner.com/key-concepts/timestamping.md)
- [Participants](https://docs.emsigner.com/key-concepts/participants.md): The key players—signers, senders, authorities, platforms, and regulators—in a secure signing process.
- [Trust Service Providers](https://docs.emsigner.com/key-concepts/trust-service-providers.md): Certified organizations that verify identities and safeguard digital transactions.
- [Authentication Methods](https://docs.emsigner.com/key-concepts/authentication-methods.md)
- [Audit Trail](https://docs.emsigner.com/key-concepts/audit-trail.md)
- [Integrations and APIs](https://docs.emsigner.com/key-concepts/integrations-and-apis.md)
- [Compliance and Legal Validity](https://docs.emsigner.com/key-concepts/compliance-and-legal-validity.md)
- [Roles and Permissions](https://docs.emsigner.com/key-concepts/roles-and-permissions.md)
- [Session](https://docs.emsigner.com/key-concepts/session.md)
- [PDF Standards, Document Sizes and Orientation](https://docs.emsigner.com/key-concepts/pdf-standards-document-sizes-and-orientation.md)
- [Billing and Wallets](https://docs.emsigner.com/key-concepts/billing-and-wallets.md)