Here is something to end the confusion.
Since it is from hyperlinked text see http://www.hindupedia.com/en/Brahm for detailed explanation.Here the underlined vowels carry the Vedic Sanskrit udātta short pitch accent. It is usual to use an acute accent symbol for this purpose.
In Vedic Sanskrit:-
Brahma (ब्रह्म) (nominative singular), brahman (ब्रह्मन्) (stem) (neuter gender) means the Great Cosmic Spirit, from root brha
Brahmānda (ब्रह्माण्ड) (nominative singular), from stems brha (to expand) + anda (egg), means universe as an expansion of a cosmic egg (Hiranyagarbha) or the macrocosm. Brahmānda Purāṇa discusses cosmogenesis. Bhāgavata Purāṇa also discusses cosmogony and fundamental principles of material nature in detail.
In later Sanskrit usage:-
Brahma (ब्रह्म) (nominative singular), brahman (stem) (neuter gender) means the concept of the transcendent and immanent ultimate reality of the One Godhead or Supreme Cosmic Spirit in Hinduism; the concept is central to Hindu philosophy, especially Vedanta; this is discussed below. Also note that the word Brahman in this sense is exceptionally treated as masculine (see the Merrill-Webster Sanskrit Dictionary). It is called "the Brahman" in English. Brahm is another variant of Brahman.
Brahmā (ब्रह्मा) (nominative singlular), Brahman (ब्रह्मन्) (stem) (masculine gender), means the deity or deva Prajāpati Brahmā. He is one of the members of the Hindu trinity and associated with creation, but does not have a cult in present day India. This is because Brahmā, the creator-god, is long-lived but not eternal i.e. Brahmā gets absorbed back into Puruṣa at the end of an aeon and is born again at the beginning of a new kalpa.
One must not confuse these with:
A brāhmaņa (ब्राह्मण) (masculine, pronounced Template:IPA-sa), is a prose commentary on the Vedic mantras—an integral part of the Vedic literature.
A brāhmaņa (ब्राह्मण) (masculine, same pronunciation as above), means priest; in this usage the word is usually rendered in English as "Brahmin". This usage is also found in the Atharva Veda. In neuter plural form, Brahmāņi. See Vedic priest
It also speaks about Brahmā in Buddhism
While "Brahmā" in Buddhist scripture, like Vedic scriptures, also refers to the non-eternal demigod, "Brāhma" is believed by scholars to refer to the eternal perfect being, and the highest stage any person can achieve is labelled as Brahma. For example in addition to Buddha's Dharma being called "Astanga Marga" and Dharmayāna, it is also addressed "Brahmayāna" because the aim is to lead one to perfection of Nirvāna. As the Samyutta Nikāya says, "This Aryan eight-fold Way may be spoken of as Brahmayāna or as Dhammayāna. Again the Buddha Dharma is equated with Brahma when" ...he has become dharma, he has become brahman." It is said that the cultivation of compassion in its purest form is "called the divine life in this world.." In this context Brahma is interpreted to mean divine. In the Suttanipāta, 656, the Buddha says that he who has won the three-fold lore and who will never be reborn is Brahma. Buddhism is compared to Brahma in other scriptures like the Majjhima Nikāya where the Dharmachakra of wheel of law is also called the Brahmachakra. The word Brahmachakra was nothing new and it was first mentioned in the Upanishads and it is believed the Buddha having received Vedic knowledge, used the term. The Majjhima-Nikāya also says that the Buddha is 'Brahmapātta' or "one who has attained Brahman"., thus outlining that when Buddha became perfected by achieving Nirvāṇa he also became Brahma.
Of Nirvāṇa, the ultimate happiness it is written "one who has attained Nirvāṇa" it is said, "may justifiably employ theological terminology.
A ) Brahmā or Brāhma - non eternal demi god responsible for initiating the beginning of universe (in Buddhism, the demi god in plane # 23 of 31 Planes)
B ) Brahman also called Para Brahman - highest Universal Principle, the ultimate reality in the universe. Now the complicated part - sometimes It maybe referred to as Brahma as in Maha Vakyas (great sentences) e.g brahma satyam jagan mithya / aham brahmāsmi / sarvam khalvidam brahma
How do we understand -- from the context. In Upanishads it is all about Brahman no matter what the spelling (also pronunciation)
C ) Brahman or Brahmana - the priestly class, also called a Brahmin (to make life easier)