Internal tools for businesses that have outgrown spreadsheets - dashboards, record keeping and the workflows around them. Whether custom is the right call depends on your situation, and often it isn't.
Most businesses reach a point where the shared spreadsheet stops coping. Several people edit it, there's no record of who changed what, everyone can see everything, and reporting becomes a manual exercise each month.
The obvious response is to build something custom, but that isn't always the sensible one. Established tools like Zoho and HubSpot are mature, inexpensive to start with, and perfectly adequate when your process resembles what they were designed around. Building from scratch makes more sense when your workflow is genuinely unusual, or when the tools available don't connect to something you depend on.
Which of those situations you're in is worth establishing before anyone writes code - and it's a short conversation, not a long one.
A general outline. What actually applies to your project is worked out together, before anything is agreed.
Looking at the actual process - who does what, in what order, and where it currently breaks down.
An honest assessment of whether something off-the-shelf would serve you better and cost less.
Agreeing how it should work and what people see, before development starts.
Developing it in stages you can review, then introducing it to the people who'll use it daily.
Describe how your team works today and where it's causing friction. I'll tell you honestly whether custom is worth it - including when an existing tool would do the job for far less.