A sibling is a brother or a sister. We often distinguish between full siblings and half siblings as the basis for some Relationship DNA tests. Full siblings will have around 50% of their genetic material in common. Each sibling receives around half of their genetic material from each of their parent. This does not include twins, who though considered siblings, if they are identical, will share all their genetic material.
Half siblings have one parent in common. We distinguish between uterine half siblings and agnate half siblings; the former means that the siblings share the mother and the latter means they share the father. Sibling relationships can be tested for with X-chromosome tests, Y-chromosome tests or STR tests which are all types of Relationship DNA tests. These tests will tell you whether you share common a common parent.