CDN is a network of servers to deliver resources to its nearest users.
When a website is using CDN, any user trying to access its resources will pass through CDN network. The nearest server that has the requested resources will deliver it to the user. Faster load speed.
Since the request didn’t even reach to the server, there’s reduced load to the server making it available to more users.
Below is an example, www.example.com is hosted in x.x.x.x server
Without CDN
Tracing route to www.example.com [x.x.x.x]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.0.100
2 1 ms 2 ms 1 ms 10.228.209.86
3 1 ms 2 ms 2 ms 122.2.174.85.static.pldt.net [122.2.174.85]
4 14 ms 14 ms 14 ms 210.213.130.186.static.pldt.net [210.213.130.186]
5 13 ms 13 ms 13 ms 210.213.130.162.static.pldt.net [210.213.130.162]
6 31 ms 31 ms 31 ms 210.14.2.102
7 35 ms 35 ms 34 ms 106.187.0.65
8 77 ms 34 ms 34 ms hkmjbb001.int-gw.kddi.ne.jp [111.87.5.25]
9 84 ms 83 ms 100 ms obpjbb205.int-gw.kddi.ne.jp [118.155.199.193]
10 80 ms 80 ms 80 ms jc-osa301.int-gw.kddi.ne.jp [113.157.227.82]
11 83 ms 83 ms 83 ms 113.157.231.42
12 84 ms 84 ms 84 ms oshrt1s-drt2-2.bb.sakura.ad.jp [157.17.146.42]
13 84 ms 84 ms 83 ms osnrt2b-hrt1s.bb.sakura.ad.jp [157.17.146.10]
14 84 ms 84 ms 85 ms osnrt3c-nrt2b.bb.sakura.ad.jp [157.17.148.2]
15 80 ms 80 ms 80 ms 210.188.211.108
16 80 ms 81 ms 81 ms x.x.x.x
Trace complete.
It took 16 hops for my request to reach www.example.com original server
With CDN
Tracing route to www.example.com [cdn ip address here]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.0.100
2 4 ms 2 ms 1 ms 10.228.209.86
3 2 ms 1 ms 1 ms 122.2.174.89.static.pldt.net [122.2.174.89]
4 15 ms 14 ms 14 ms 210.213.130.194.static.pldt.net [210.213.130.194]
5 14 ms 14 ms 14 ms 210.213.130.109.static.pldt.net [210.213.130.109]
6 14 ms 16 ms 14 ms 210.14.3.102
7 14 ms 15 ms 14 ms [cdn ip address here]
Trace complete.
It only took 7 hops to reach www.example.com using CDN and no request was made to its original server. So faster content delivery and reduced load to the original server.