Essentially shared IP hosting means that your website is sharing a server with other websites.
There is good and bad to this, but mostly it’s fairly invisible.
As you can imagine, this makes the barrier to entry for startup websites quite low.
The bad news is that it’s quite easy to outgrow this kind of hosting package.
Any changes to your server made by the hosting company benefiting the others might not necessarily benefit you and large spikes of traffic to the other sites can bring your site down as well.
Getting your own IP address also allows you to expand your website beyond a regular blog or website, for example hosting a web service of some kind.
For regular websites I definitely recommend looking at shared hosting and upgrading to a dedicated IP address when the time comes. Especially when testing new ideas, hosting packages such as these are more than adequate.