This will set the benchmark by which your end product can be judged. The measurability of this can be in terms of time scales, resources, targets and goals.
Some examples could be to automate the workflow of your organisation, to integrate with other systems or meet new scalability requirements.
This describes the interfaces that the product must support. For example, it could define a numeric or date entry for a field, in a form. Or the mapping and workflow of your screens or user access.
Nowadays, the majority of organisations, if not all, are required to follow some level of compliance. This could be to adhere to the GDPR data regulation, to the sales of goods act, or another legal requirement.
If so, the application may need to work in a certain way. It could involve adding a GDPR notice to a registration form, data being transmitted in a certain way, or something else.
Defining your requirements helps to identify the behaviour, attributes and properties of the future system. Therefore, the main task of any functional requirement document is to ensure that all stakeholders understand what is needed and what is expected.