A Mericlone is an artificially produced clone of an orchid which is deemed to be of significant quality to merit this kind of replication. They are produced by taking a small piece of tissue from the specimen plant, mincing the piece into tiny pieces and then growing the tissue in a laboratory into multiples of identical plants. The advantage of buying and growing mericlones is that you know exactly what you are getting—the plant and the flower will be identical to the parent. You will be getting an outstanding example of an orchid flower. The disadvantage is that mericlones are generally more expensive since they are more expensive to produce.
For the new orchid grower, I would recommend buying blooming size mericlones if you can afford them. If you buy them already blooming, you will have the instant gratification of enjoying the flowers and you will know what kind of plant and when it will bloom. If blooming size plants are out of your budget, try to purchase “Near Blooming Size” mericlones of plants that produce flowers that appeal to you from a repeatable nursery. It may take a couple of years for them to bloom, but you will appreciate them for that!
I do not suggest that you start out with seedlings as a new grower, even though they are less expensive. They can take up to seven years (depending upon the genus—sometimes longer) to flower and they are rather delicate. Mature plants are much more likely to survive while you are learning to care for them and if you are good to them, they will flower for you on schedule.