Seo as I understand

1. Seo i.e. Search Engine Optimization.
2. Various search engines are: Google, Yahoo & Bing.
3. Like in Google whatever we type to search acts as a keyword phrase. For example, I  typed ceiling designs in Google so ceiling designs is our keyword.

4. Various results are appeared on the screen. More than 48 lacs results appeared for ceiling designs.

5. Every page wants to come on the top but some techniques are to be used so that they should come on the top and these techniques are known as Search Engine Optimization Techniques.

6. Various SEO tehniques are :

(a) URL Names: include relevant keywords. As I have opened Drawing Room Ceiling Designs URL name appeared is http://www.gharexpert.com/control/trim.is

(b) Meta Tags- Title & Description: Each page should have different title with 2 or 3 of keywords at beginning. As I studied in Drawing Room Ceiling Designs  the title names appeared as: Drawing Room Ceiling Designs | Ceiling Designs| False Ceiling Designs| Living Rooms Ceiling| Pop Ceiling Designs. And it's description is Drawing Room Ceilings can change the interior of the rooms.

(c) Keyword Density: It is defined as the percentage of times the keyword phrase used in the webpage text.For example, If we have webpage of 100 words including headings,etc and we have keyword phrase that is on the page 5 times then we have keyword density of only 5%

(d) H1 Tag: Displays the heading of the webpage text. For example, Drawing Room Ceiling Design is the heading. 
(e)H2,H3 Tags:  Displays the sub-headings. For example, Ceiling Moldings and Domes represent the sub-heading