Guest posting is what people do on other websites which may have high domain authority and may have a large audience to promote their blog to a bigger audience. But you will not have control of the content and usually, the website owner who accepts guest posting first approves your content before publishing on their website. But they are a great source to drive traffic and make backlinks.
Blog posting is either done on your own website or post published by you on any topic where the content is own by you and also blog posting is considered when you post a blog on social blogging sites.It is also a great source of getting backlinks.
Lucaspayne makes great points about the differences between guest posting and blog posting.
If you are looking to build your own content on your website, that is blog posting. However, if you are looking to generate backlinks to your website or get your name/brand out there, guest posting on someone else's site is a great method of doing this.
One of the best ways to start generating traffic to your website / business is by offering something of value to others in the form of a guest post on someone else's blog with useful content.
Hopefully this helps.
it is literally a very simple answer - Guest posting - when you write blog for other site as a guest this is guest posting
while Blog posting - is writing and posting blog post for your site or if you are working for others.
Guest post is not sure to be posted or It depends on other whether he/she will post your aticle or not while the Blog post is sure to be posted on the site or it depends on you whether you will post the aricle or not.