Blender is an incredibly powerful open-source (and thereby totally free!) modelling, animation and rendering program. But for all that power, it has a rather steep learning curve. Fortunately, it has a massive community of folks churning out fantastic tutorials and help for everyone from total beginners up to pro-grade Hollywood experts.
Blender can generate some powerful architectural visualizations and lighting renderings, either via its science-accurate Cycles rendering engine or its powerful live-rendered Eevee engine. If you’re interested, I suggest checking out Andrew Price at Blender Guru and his fantastic YouTube channel.
As one of his series, Price put together a nice set of videos exploring fundamentals of lighting for typical rendering compositions. It is actually quite good to share with your “non-lighting” friends!
If you want a rather in-depth tutorial on archviz specifically, check out his 3 part series:
And if you just want a fun, total newbie intro to Blender, his “Donut” series is great!