Short answer
High bandwidth helps large downloads, but latency, WiFi, server capacity and congestion affect how fast the internet feels.
Download and upload
Download is used when receiving data. Upload is used for video calls, backups, cloud storage and sending files.
Why WiFi can be the bottleneck
Distance, walls, interference and older equipment can make WiFi slower than the subscription.
Measure correctly
Test with cable when possible, stop heavy transfers and compare several servers before judging the connection.
Common questions
Is Mbps the same as MB/s?
No. 8 megabits are roughly 1 megabyte.
Why do I not get full speed?
WiFi, the server you connect to, equipment and congestion can limit speed.