Conception
A chart describes tendencies in a traditional system. It cannot decide health, money, law, marriage or children.
In the classical sources
二曰受胎，天地气交，氤氲造物，其物在地中萌芽，始有其气，如人受父母之气也
Second is Conception: the breaths of heaven and earth mingle and, in a warm haze, make things. The thing sprouts within the ground and first has its breath, as a person receives the breath of father and mother.
三命通會 卷二
About this stage
胎 is the embryo. 三命提要 says heaven and earth mix their breath and something starts to sprout below ground, as a child takes breath from two parents. It falls for 甲 at 酉, for 丙 at 子, for 庚 at 卯 and for 壬 at 午, right after each stem's 絕 point.
As a position this is a small early foothold, with nothing visible yet and something already there. 三命通會 sets it among the four stages it calls valued, beside Growth, Emperor and the storehouse, a high ranking for something so new. The name uses the language of pregnancy and refers only to a step in a stem's cycle.
Where this text comes from
The order of the twelve stages follows 五行大義 volume 2 and 三命通會 volume 2 on Wikisource. The calculator uses that order for wood, fire, metal and water. Works disagree about earth.
The English name follows common modern usage. The wording here is our own plain summary.