Switching is a practice which allows a Tulpa to interact directly with the physical world via the creator's body. Strictly speaking, switching involves the host and tulpa literally switching places—with the tulpa taking control of the body, and the host detaching from the body's senses and immersing themself completely in the wonderland—but "switching" has also come to refer more generally to any method of allowing the tulpa to take control, including Possession and eclipsing.
Eclipsing is a form of switching which involves blurring the lines between the host and tulpa's identities. It can be thought of as a temporary merge, during which the host and tulpa perceive themselves as one individual rather than two. The merged consciousness may retain the tulpa's identity and personality (with the host's being suppressed) or occupy a fluid state where the dominant personality shifts between that of the host and tulpa. In either case, the host retains complete sensory awareness and memory of the experience but partially or fully gives up their sense of self for the duration.
Eclipsing is a temporary state. Talking to your eclipsed partner will induce separation, as holding a conversation involves recognizing yourselves as separate individuals.