He’s making 10 sales a month. Even if I wrote pants-droppingly good copy for him and increased his sales by 200% — a % lift any CRO expert would blog & tweet about — this would only generate an extra $200 per month for his business:
A blog is an online journal; searching the word on Google will give you many examples. To blog is to write in a blog.
Twitter is an online social networking site where people post tweets, short messages. Again, Google it and head to Twitter for examples. To tweet is to write one or more tweets.
Overall, the phrase refers to sharing something on social media - in this case, because the 200% increase is important or unusual enough to share.