Any article rewriter or paraphrasing tool basically scans through the content you provide it in order to look for all the words that it can replace with suitable synonyms or substitutes. Every replaced word will appear bold and highlighted in a colorful text. Clicking on the word will give you details such as original word or other suggestions, you also have an option to add your own word. By clicking on the original word, you can go back to original.
For a blogger who has to publish multiple blogs on daily basis, it is tough for them to write unique content, especially when writing on same topics. In that case, spin bot tool could be used to avoid self-plagiarism and to maintain the quality on blog posts. As spinbot change synonym automatically but you can pick the most relevant synonym using out tool.