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

# Key concepts

## Folder

Folders allow documents upload. A folder can be created, named, or deleted by a signature initiator. Multiple documents in the folder can be signed within a single signing session.

Folders are visible for the signing initiator (so the owner of a folder) and all defined signees.

Moreover, one folder can store many documents at different signing stages.

However, signees are allowed to have an access and sign only documents being delegated for them within a folder.

## Document

It is a PDF file that is dedicated for signing. A document (PDF) can be uploaded, forwarded for signing (as a link) to another person, signed, deleted or downloaded through API.

## Signature Types

There are three electronic signatures available on **SIGNIUS Professional platform**: **ADVANCED**, **ADVANCED & KYC** and **QUALIFIED**.

<div align="left"><figure><img src="/files/4mytY0BI7N2jnFFXbMtW" alt=""><figcaption></figcaption></figure></div>

**ADVANCED signature** - phone number is validated (equivalent to **EASY** signature in our API).

<div align="left"><figure><img src="/files/DCtVBaCa5Ii2B7mkKTSk" alt=""><figcaption></figcaption></figure></div>

**ADVANCED & KYC signature** - strong identity verification of a signee is obligatory e.g. through e-banking (equivalent to **ADVANCED** signature in our API).

<div align="left"><figure><img src="/files/96kziv8nid1aNXFtz4ha" alt=""><figcaption></figcaption></figure></div>

**QUALIFIED signature** - uppermost identity verification of a signee is obligatory e.g. through a certified video-call or mobile app self-video (named also **QUALIFIED** signature according to our API).

#### Identity Verification

**IDENTITY VERIFICATION** is a process, which involves verifying the identity of an individual applying for a digital signature. SIGNIUS offers integrated verification technologies, which enable to verify the identity of a person immediately online. Our platform offers various \&user-friendly identity verifications methods in multiple languages.

In the integration process there is also a possibility to choose test verification (this is an option allowing to skip a real identity check).

Moreover, as the data from the identity verification are stored, they can be either transferred, if requested.

<div align="left"><figure><img src="/files/OGExl6v31gRahibyzmjO" alt=""><figcaption></figcaption></figure></div>

## Representation of signatures

In the signing process, the signature is embedded in the pdf document electronic layer. Besides that we allow to create the graphical representation of signatures.

There are two different options possible:

#### Visualisation on the first page of the document <a href="#visualisation-on-the-first-page-of-the-document" id="visualisation-on-the-first-page-of-the-document"></a>

In the sidebar of the first document page, a list of the persons who signed the document will appear along with the time of their signatures. If this option is chosen, it will not interferre with signatures (e.g. from other suppliers) already embedded in the file. **This process does not modify the signed document.**&#x20;

<div align="left"><figure><img src="/files/a97zCo4267OccInUuspI" alt=""><figcaption></figcaption></figure></div>

#### Additional page at the end of the document <a href="#additional-page-at-the-end-of-the-document" id="additional-page-at-the-end-of-the-document"></a>

The page added at the end of the document will contain a list of all persons who signed the document along with the time of their signatures. If signatures have already been placed on the document before uploading it to SIGNIUS, **we recommend not to add an additional page, because selecting this option will modify document and will result in invalidation of previously placed signatures.**

<div align="left"><figure><img src="/files/KkMrVJKki9DihJxTGE7L" alt=""><figcaption></figcaption></figure></div>


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