The web development process is usually broken up into 7 steps:
Gathering requirement - The first step is understanding the goal of your website and how to best address them.
Researching industry trends - Then, many agencies will research your industry to understand your competition and incorporate relevant trends into your site.
Creating wireframes - From there, designers will create wireframes, or a blueprint that visualizes the layout of the site.
Creating visual designs - Once the layout is set, visual designers bring wireframes to life by adding aesthetic elements of the site: images, color, fonts etc.
Development - Then the site gets developed or built.
Testing - Testers, or occasionally the developers themselves, will ensure that the site functions as it should.
Deployment - Lastly, the site is launched and can be used publicly.