Can I create leads in Salesforce and embed them in my website or in Salesforce?

Yes- you can!
You can, most definitely,  use FormTitan to create leads in your Salesforce account.

Basically, It works like this:
- You will need to create a web-to lead form. Drag and drop your elements onto the canvas, fix the layout and the styling.
- You will then need to configure a Salesforce integration. The integration is Bi directional, so you can read from SF as well as write in SF objects.
- In order to create leads you will need to choose the Push integration, which allows you to write data in salesforce objects.
- You will then need to choose the "Create" action and map your form fields to the "Leads" object in Salesforce.
- After the integration is set up, you will need to publish the form in order to use it.
- Simply choose the desired publish method, copy the generated code and use it. 
- Visitors in Salesforce or in your website will enter data in the form and once they press the 'submit' button the data will be automatically pushed to Salesforce as a new lead.
In order to embed the form in your website you will need to use the Embed or Iframe option. In order to embed the form in Salesforce you will need to use the form URL and follow these instructions.