A website explains a business and helps people take an action. A web application helps people do something: manage records, submit a workflow, calculate an outcome, collaborate, book, buy, or sign in.
Look for the repeated task
If your team is moving information between spreadsheets, email, and dashboards every day, there may be a workflow worth designing. Start by mapping the people, inputs, decisions, permissions, and outputs. Sometimes a better website and a simpler form solve the real issue; sometimes the process deserves an application.
Build the smallest useful version
Define the core task, failure cases, data ownership, and success measure before adding accounts or automation. Good applications make the hard path clearer rather than adding technology for its own sake.
Explore web application development when the work is interactive and persistent.