Doula is originally a Greek word that means "woman servant" or "woman caregiver".
Our current use of the word typically centres around someone who is experienced in supporting childbirth and supports parents during pregnancy, labour and birth. Postnatal doulas support into the postnatal period. This is the area that most doulas work in - some offer both birth and postnatal support, and some offer only one or the other.
A full-spectrum doula has expanded that circle of care to also include other reproductive scenarios, particularly around those who have chosen to terminate their pregnancy, but also supporting those who are suffering infertility, going through IVF, adopting a child, having a baby via surrogacy or other scenarios.
End of life doulas support those who are preparing to die. There are many similarities between birth and death, such as the medicalisation of both events and lack of information about options, as well as death being a topic that is often avoided because it's "too morbid".