Search volume; is the daily and monthly search rates of a keyword or a keyword group on a search engine.
Keyword competition; determines the difficulty level of the SEO work that will done for the keyword that has been made.
For a website that will be opened for the first time, it is not preferable to do SEO works on high volume and high competition words. To obtain success with these challenging words, putting weight on just a single word may not give the desired results. Actually, the authority of the website and backlink works determine the progress of this work. For this reason, it is more logical to choose low-competition and medium or high search volume keywords for this kind of websites.